Vibration control of rotating disc

ABSTRACT

A method for dynamic electrical testing of head gimbal assemblies may include initiating an automated continuous process that includes selecting an unmounted head gimbal assembly; aligning the unmounted head gimbal assembly; loading the unmounted head gimbal assembly to a disc; and testing the unmounted head gimbal assembly.

This application is a continuation of U.S. patent application Ser. No.11/056,337, filed Feb. 11, 2005, which claims the benefit of U.S.Provisional Application No. 60/544,040, filed Feb. 12, 2004, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to methods and apparatus for manipulating,retaining and electrically testing small parts, typically smallelectronic components. More particularly, the invention relates tomethods and apparatus for testing head gimbal assemblies used incomputer disc drives.

BACKGROUND

Prior to attaching a head gimbal assembly (HGA) into a hard disc drive,it is desirable to dynamically test the functionality of the read andwrite transducers that reside on the head gimbal assembly so thatdefective HGAs may be identified and sorted. Such testing can includepreliminary activities to align, configure, and prepare the HGA fortesting, followed by the actual electrical test of the HGA. Because HGAsare typically small, fragile, and contain sensitive electroniccomponents, they are susceptible to mechanical stress, electro-staticdischarge (ESD), environmental contamination, and other handling-relatedissues.

To avoid these handling-related issues, current systems mount the HGA onan intermediate mounting fixture that supports the HGA throughout thetesting process. An operator may manually place an HGA into an alignmenttool that sets the orientation of the HGA to an intermediate mountingfixture. The alignment of the HGA to the intermediate mounting fixtureis important because it helps determine the orientation of the HGA withrespect to a disc during dynamic electrical testing. After alignment, ahead set operation is performed in which the HGA and the intermediatemounting fixture are manually passed through a magnetic field toproperly set the direction of the magnetic domains of the read and writetransducers inside the head of the HGA.

Initially, the HGA's read and write transducers are electrically shortedtogether with a shunt tab, which resides on a flex circuit of the HGAand protects the HGA from ESD damage by ensuring that the components areheld at a common voltage potential. This shunt tab must be broken orremoved prior to testing the HGA. In current systems, the shunt tab ismanually broken or cut off before the HGA is loaded into the electricaltester. After its removal, the HGA becomes extremely sensitive to ESDdamage. Positioning the flex circuit for removal of the shunt tab ischallenging because the flex circuit is flexible, and its position canvary over a relatively wide area. Additionally, flex circuits may havean inherent bend or twist, further complicating flex circuitpositioning. In current systems, the intermediate mounting fixtures havepositioning pins to precisely locate the flex circuit for de-shunting.

When the HGA is ready for electrical test, an operator can manually pickthe HGA from a tray by grasping the intermediate mounting fixture andloading the HGA onto a dynamic electrical tester. During the dynamicelectrical test procedure, the HGA's flex circuit makes interconnectwith the dynamic electrical tester's preamplifier, the HGA is loaded toa test disc, and the read and write transducers on the HGA are tested.Using this method of HGA manipulation and electrical testing requires anew intermediate mounting fixture to be designed and fabricated for eachnew HGA type. The intermediate mounting fixture generally consists of aclamping mechanism to hold the HGA base plate, a set of pins to locatethe HGA flex circuit for interconnect, and a set of holes and pins tolocate the intermediate mounting fixture at the various operations,including dynamic electrical test.

The clamping mechanism of the intermediate mounting fixture that holdsthe HGA base plate during electrical test has several requirements. Asthe bit density in disc drives increases, in operation the drive headsmust fly lower with respect to the disc. This requires tightertolerances for the HGA's orientation. Errors in the orientationinfluence Roll Static Attitude (RSA) and Pitch Static Attitude (PSA),which affect the HGA's ability to load to the disc and its flycharacteristics after loading. RSA and PSA are effectively the head'sstatic orientation relative to the disc. To ensure that the HGA'sperformance is consistent for both electrical testing and operation ofthe drive after installation, it is important the HGA be similarlyconstrained during both functions.

During operation of the drive, it is optimal for the HGA's base plate tobe pulled down with approximately three-to-seven pounds of forcerelative to a reference surface and fastened by swaging a boss hole inthe HGA to a rotary arm in the drive. In the past, the HGA's base platehas been held by attaching the HGA to an intermediate mounting fixtureand then placing the intermediate mounting fixture on the tester. Thismay require manually screwing the HGA to the intermediate mountingfixture before placing it on the tester. While this is an accuratemethod of mounting and provides the needed downward force, it is verylabor intensive and adds an extra amount of error contributed by thefixture to the testing process.

Another method of attaching the base plate to an intermediate mountingfixture involves using a flexure clamp jaw that clamps the HGA's bosshole. While this is less labor intensive than manually screwing the HGAin place, it still requires extensive manual handling of the part. Italso does not provide any downward force, which leaves the base plateunconstrained and not flat. This negatively affects the test results.

Still another method includes mounting the HGA to an intermediatemounting fixture that holds the HGA by pinching it with a clamp betweenthe back of the base plate and a pin through a swage hole present in theHGA. This method also does not provide sufficient downward force, butforces the back edge of the base plate to align to the clamp. Becausethe back edge of the base plate is not a controlled edge, this may causemisalignment during the testing process.

All of the above-described methods are difficult to automate and havecosts associated with loading, purchasing, and maintaining the extrafixtures on which the HGAs are mounted. The intermediate mountingfixtures also create a larger mass and require an additional mechanicalinterface, both of which create another potential source of error orvibration during the dynamic electric test.

In current systems, pins on the intermediate mounting fixture align theinterconnection pads on the HGA's flex circuit with the dynamic electrictester's preamplifier contacts so that interconnection between the twois achieved. This alignment is necessary because the flex circuit isflexible, which permits the location of the interconnection pads to varyover a relatively wide area. After the flex circuit is constrained forinterconnection, the intermediate mounting fixture, which holds the HGA,is loaded onto the tester.

The set of holes and pins used to align the intermediate mountingfixture for testing the HGA affects Reader Writer Offset (RWO), which isan important measurement in the dynamic electrical test. RWO is thedistance a read/write head jogs to read a track that it has justwritten. The RWO is a function of the skew angle of the head, which isthe angle of the head relative to the center of the disc on the x-yplane, the reader-to-writer separation distance, and thereader-to-writer alignment on the head. Because RWO data is used toverify that the reader-to-writer separation and alignment are within thetolerance limits of the process controls, the process of loading the HGAto disc should be carefully controlled so that the position of the HGA'sskew angle is both accurate and repeatable.

Challenges to accurately loading an HGA to a disc include maintainingthe HGA's orientation precisely from the moment it is put on the loadmechanism until it is loaded to the disc. Also, one must ensure that thestructure stiffness of the load mechanism does not contribute topositional error during test. Additionally, the process of loading theHGA must be carefully controlled to prevent damage to the HGA. Forinstance, the HGA cannot be bent significantly beyond its normaloperating state. It also must be presented to the disc at a shallowenough angle to prevent any features from unintentionally contacting thedisc during loading.

The cost effectiveness of the loader is not only measured in directhardware costs due to damaged parts, but also in its cost effectivenesson the testing process. For instance, costs associated with the loaderinclude the down time for the tester when there are changes in productconfiguration. Another cost includes the cost of testing media, which isone of the greatest costs in HGA testing. HGAs can crash a disc forseveral reasons during test including contamination of the media,non-optimal load orientation of the HGA, and HGAs with extreme orout-of-specification roll or pitch values.

Currently, load mechanisms typically include vertical translatingstages, ramp loads, or tilt mechanisms. The vertical translating stagemaintains the base plate of the HGA parallel to the disc and lifts theHGA to the disc. New generations of HGAs have features on the load beambeyond the head that contact the disc before the head and can damage thedisc. This can result in a limited number of loads before the HGA ormedia are crashed. The ramp load mechanism works well in the drive, butit is difficult to use in the testing process. The ramp is typicallyfixed in location at the parameter of the disc, which limits the loadingof the HGA to only one radius. Once that radius is crashed, that discmust be discarded. Ramp loading also can result in damage to the HGAfrom the sliding action across the ramp if the appropriate materials orsurface finish are not used. However, use of the ramp enables loadingthe HGA to the disc at a shallower angle.

The third and often used loading method utilizes a tilting mechanism. Astage pivots, lowering the HGA below the surface of the disc. Once theHGA is moved into position under the disc surface, the HGA is pivoted upto the disc surface. One of the challenges of this mechanism is where tolocate the hinge. The ideal location of the pivot point is near the bendin the HGA. The hinge, however, needs to be in real space and cannotinhibit positioning the HGA at various places on the disc. Miniaturizedloaders with small pivot bearings have been used, but it is difficult toachieve the required structural stiffness and maintain all the tighttolerance required with a small structure and still provide room toaccess the HGA with an electrical interconnection. Though the HGA can beloaded at an angle shallower than the vertical load, it does notsufficiently reduce stresses to the HGA during load.

Once the HGA's head is loaded to the disc, there are still many sourcesof positional disturbance that can affect the effective track densityduring testing. For instance, disc flutter is a result of exciting adisc at the disc's natural resonant frequencies. Internal and externalsources, such as spindle motor vibrations or external air turbulence andacoustic vibrations, may create vibrations that excite a disc and createdisc flutter. The flutter is primarily a vertical modulation of the discwhile the disc is rotating. The modulation creates bends in the disc.The compliance in the HGA load beam allows the head to followundulations of the disk, but because the base plate of the HGA is heldfixed relative to an external reference there may be a small error. Thiserror is significant at current and higher track densities. The radialmotion contributes to the total asynchronous runout, which exists whenposition errors are asynchronous, or do not repeat on each discrevolution.

Some current systems use devices between the spindle motor and the discto reduce flutter. In these systems, one must test the HGA's head on thedisc side that is opposite of these devices. Common approaches eitherrequire testing the top surface of the disc, which necessitates that thespindle protrude down into the test stand, or inverting the spindle thatholds the disc so that the testing can be performed on the bottomsurface of the disc. Both approaches have disadvantages. Systems thattest the top surface are at a disadvantage from a part handlingstandpoint because testing on the bottom surface is considered morecompatible with how the HGA is presented to the HGA tester.Additionally, placing a disc on the spindle is more difficult in currentsystems that test the top surface because of the close proximity of theflutter reduction device to the seated disc. Current testers may needextra mechanisms, such as guide fingers, to guide the disc to its finalposition. Current systems that test the bottom surface of the disc alsohave disadvantages because they typically invert the spindle, whichcreates a number of structure challenges in order to maintain therequired rigidity and access for disc changes and other service needs.

During dynamic electrical testing, the intermediate HGA mounting fixturealso has a large effect on the test and the test results. Theintermediate mounting fixture can add to the stack-up tolerance relatedto the HGA's z-height causing small shifts in fly height. By increasingthe mass that the tester micro-positioner must move while testing, thepresence of the intermediate mounting fixture can lead to lower dynamicelectrical tester track per inch (TPI) capability. The size of theintermediate mounting fixture also can limit the radii and skewlocations that the HGA is loaded onto and unloaded from the disc. Bylimiting the load radii and skew options, the tester may use more mediaand take more time to load the HGA, which decreases the number of HGAstested in a given period of time.

SUMMARY

In one aspect, the invention is a computer-controlled, automated methodand apparatus for loading, aligning, and testing an HGA that is notmounted on an intermediate mounting fixture (referred to herein as anunmounted HGA). Advantages of this apparatus and method include, forexample, avoiding time and capital costs associated with testing an HGAmounted on an intermediate mounting fixture; and avoiding time andcapital costs associated with maintaining the intermediate mountingfixture. The method and apparatus also improve the efficiency, accuracy,precision, and repeatability of aligning an HGA for testing.

In another aspect, the invention is a method and apparatus to provide amore efficient method to de-shunt and headset an unmounted HGA. In yetanother aspect, the invention is an automated method and apparatus forstraightening an unmounted HGA's flex circuit without causing damageduring de-shunting.

Also, the invention is a method and apparatus that provides acomputer-controlled, automated method to accurately locate and break theshunt tab on an unmounted HGA.

The advantages of these methods also include: avoiding contact betweenthe disc and HGA clamping mechanism; providing a clamping force on theHGA similar to the force applied after the HGA is installed in a drive;improving the efficiency of accurately aligning the HGA for testing; andminimizing additional positional error or vibration by lowering the massrequired to hold the HGA and eliminating extra mechanical interfaces.

In yet another aspect, the invention also includes a computer-controlledautomated method and apparatus for correcting the positional errors ofthe flex circuit on an unmounted HGA prior to interconnect with apre-amplifier. This method and apparatus overcomes errors caused by thediffering heights of the pre-amplifier contacts and the flex circuitlayers; and improves the clamping mechanism for pressing a flex circuitagainst a preamplifier's contacts.

Other aspects include: providing a HGA loader that minimizes head angleto disc during loading; permitting loading of an HGA to a disc atmultiple radii; providing lock down of the loading device during test;improving the accuracy and cost efficiency of loading an HGA to a disc;reducing the time required to load an HGA; and providing a device thateasily accommodates different HGA geometries.

In another aspect, the invention includes a method and apparatus forimproving suppression of disc flutter; providing more efficient loadingof media; providing more efficient access to the underside of the discduring testing; and providing more efficient access to the structuressurrounding the disc for servicing.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view of an unmounted HGA;

FIG. 1B is a schematic side view of an HGA;

FIG. 2 is a block diagram of an exemplary device that can test unmountedHGAs;

FIG. 2A is one embodiment of a device that can test unmounted HGAs;

FIG. 2B is an enlarged view of the device in FIG. 2A without a portionof its support structure.

FIG. 3 is one embodiment of a tray load and unload area of the deviceshown in FIGS. 2A and 2B.

FIG. 4 is one embodiment of a précising nest;

FIG. 4A is a more detailed view of flex-on-suspension (FOS) alignersshown in FIG. 4;

FIG. 4B is one embodiment of a précising area including anelectromagnet, the précising nest, and a device for de-shunting the HGAshown in FIGS. 1A and 1B;

FIG. 4C is a more detailed view of a portion of the de-shunting deviceshown in FIG. 4B;

FIG. 4D is a diagram of one embodiment of a de-shunt pin used forde-shunting.

FIG. 5 is one embodiment of a portion of a test area.

FIG. 5A is a sectional view of an embodiment of a nest with a colletassembly;

FIG. 5B is an exploded view of the collet assembly shown in FIG. 5A;

FIG. 6 is one embodiment of a clamp wing assembly that may be used tohold the FOS against an electrical contact;

FIG. 6A is one embodiment of the clamp wing assembly in the state ofholding the FOS against the electrical contact.

FIG. 6B is one embodiment of the electrical contact using gold blocks.

FIG. 6C is another embodiment of the electrical contact using asolderless connector.

FIG. 6D is a more detailed view of the electrical connector shown inFIG. 6C with optional features.

FIG. 6E is an alternative embodiment of the electrical connector withpairs of conductors.

FIG. 7 is one embodiment of a tail pusher and a tail flattener;

FIG. 8 is one embodiment of a four bar loader;

FIG. 8A is the device shown in FIG. 8 tilted below the disc inpreparation for testing the HGA;

FIG. 8B is the device shown in FIG. 8 moved under the disc;

FIG. 8C is the device shown in FIG. 8 loaded to the disc;

FIG. 9 is one embodiment of a disc flutter control device;

FIG. 10 is a section view of embodiment shown in FIG. 9;

FIG. 11A is air flow over the disc without the disc flutter controldevice shown in FIG. 9; and

FIG. 11B is air flow over the disc with the disc flutter control deviceshown in FIG. 9.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

As shown in FIG. 1A, the basic components of an HGA 100 are a head 102,a load beam 104, a tooling hole 106, a base plate 108, a boss hole 110with an angled surface 110 a, and a flex circuit 112 with a flex circuitpads 118 and a shunt tab 114. The head 102 flies above the surface of adisc and contains the read and write transducers. As shown in FIG. 1B,the load beam 104 is a thin, metal structure that has a bend, whichprovides the spring force to hold the HGA adjacent to the disc duringoperation. The angle of the bend with respect to the base plate 108 isthe free state angle 116.

FIG. 1A shows the base plate 108, which is retained during testing topermit manipulation and alignment of the HGA assembly, and eventually,is mechanically fastened into a disc drive. The boss hole 110 and thetooling hole 106 are used for aligning the HGA. The flex circuit 112 andits components will subsequently be described in more detail.

To eliminate the intermediate mounting fixture from the dynamicelectrical testing of HGAs, all of the functions that the intermediatemounting fixture completed now must be completed through some means thatdoes not travel along with the HGA. The absence of an intermediatemounting fixture in a process is referred to herein as an unmountedprocess. However, even in an unmounted process, the test method andapparatus must still pick, align, headset, de-shunt, load onto a testnest, interconnect with a preamplifier, and load the HGA to the disc.The small size and fragility of the HGA makes it necessary that all ofthose operations be mechanically controlled.

One embodiment of a device that does not use an intermediate mountingfixture is the unmounted HGA tester (UHGAT) 200 shown in the blockdiagram of FIG. 2. The UHGAT 200 includes, but is not limited to, fourmain functional areas. Three of the functional areas are process areas:the tray load/unload area 202, the précising area 204 including aprécising nest 210, which aligns, de-shunts, and headsets the HGAs, andthe test area 206 including a test nest 212, which interconnects the HGAwith a preamplifier and loads the HGA to the disc. The fourth functionalarea, the control area 208, controls the UHGAT automation and eliminatesthe need for operator intervention during the UHGAT dynamic electricaltest.

FIG. 2A shows a drawing of one embodiment 201 of the UHGAT device 200with support structures for a fan 209 and actuators described later ingreater detail. The UHGAT device 201 shown in the figure includes thetray load/unload area 202, the précising area 204, and the test area206. The control area 208 is not shown in FIG. 2A. The control area 208includes a computer, a display with a user interface, an input device,and circuit boards with embedded controllers. An operator may use theuser interface to specify settings for the testing process, such as thegauss level during headset at the précising nest 210, and initiatestesting with the UHGAT software installed on the computer. Control ofthe UHGAT machinery is accomplished through the embedded controllers andthe UHGAT software. The UHGAT automation ties together the threeprocessing areas by controlling the transfer of HGAs from the trayload/unload area 202 to the précising area 204, and then to the testarea 206 before the automation finally brings the HGA back to the trayload/unload area 202 as illustrated in FIG. 2 by the arrows 203, 205,and 207, respectively.

FIG. 2B is an enlarged view of the device 201 in FIG. 2A without aportion of its support structure. With the removal of the supportstructure, one may more clearly see the three processing areas. In theembodiment shown, there may be a tray 300 in the tray load/unload area202. The précising nest 210 may be in the précising area 204, and thetest nest 212 and a disk 810 may be in the test area 206. Additionally,automation that moves the HGAs to and from each area may consist of twoend effectors, a first end effector 304 and second end effector 308,that use vacuums to hold the HGAs while they are transferred.

FIG. 3 shows one embodiment of the tray load/unload area 202 of thedevice 201. The first and second end effectors 304 and 308 are eachattached to a first and second pneumatic linear actuator (not shown nFIG. 3), respectively, which are attached to a main pneumatic linearactuator (not shown in FIG. 3). The pneumatic linear actuators move theend effectors in the ‘z’ direction and are controlled using conventionaltechniques with solenoid valves, hall sensors and flow controls. Themain pneumatic linear actuator is attached to a linear motor positioningstage (not shown) and is also controlled using conventional techniquesby a solenoid valve, hall sensors an d flow controls. More expensive andcomplicated servo controlled actuators could replace any of thepneumatic linear actuators if the higher precision and velocity controlcould justify the increased cost. The linear motor positioning stagemoves the first and second end effectors 304, 308 between the trayload/unload area 202, the précising area 204, and the test area 206. Thelinear motor positioning stage may be a high precision and high-speedservo-controlled actuator. A very accurate high-speed servo controlledactuator is needed to ensure that the HGA is delivered to the correctposition very accurately in a minimum amount of time.

As shown in FIG. 3, the first processing area is the tray load/unloadarea 202 where an operator loads and unloads trays containing HGAs.After the tray load/unload area 202 is loaded with the tray 300, whichmay be done manually by an operator or using an automated placementprocess, the UHGAT automatically identifies the HGAs by reading a radiofrequency (RF) tag 301 associated with or placed inside the tray. Oncethe trays have been loaded, the UHGAT picks the HGA from the tray usinga vacuum 322 of the first end effector 304.

When an HGA is removed from the tray it is moved to a second processingarea, the précising area 204, where it is aligned on the précising nest210, de-shunted and headset. After these operations are complete, theHGA is moved using the end effector 304 from the précising area 204 to athird processing area, the test area 206. During transfer from theprécising area to the test area, the HGA maintains the alignment set onthe précising nest 210. After placement on the test nest 212, the flexcircuit 112 (See FIG. 1A) is aligned and moved down to make interconnectwith a preamplifier. The preamplifier contacts are large flat goldcontacts that cover the tolerance range of the flex circuit's 112position.

Next, the linear motion positioning stage moves both first end effector304 and second end effector 308 back to the tray load/unload area 202.The next HGA is picked from the tray and brought to the précising area204. Then the first HGA is loaded to the disc using a four bar loader800 (See, for example, FIG. 8) and dynamic electrical testing proceeds.After electrical testing is complete, second end effector 308 removesthe first HGA from the test nest 212. The next HGA, already on first endeffector 304, is loaded onto the test nest 212. The same sequencecontinues until all of the parts in the trays have been tested.

The following text describes each of the three functional process areasin more detail beginning with the tray load/unload area 202. The stepsthat may occur include placing a tray in the load/unload area andinitiating the automated testing process. The tray's presence is sensed,and the tray's RF tag is read. Based on the read information, untestedHGAs are selected for testing and the testing process can be configuredbased on the type of HGA in the tray. The tray's lid is opened, and anHGA is picked up off the tray. Next, the HGA is moved from the trayload/unload area 202 to the précising area 204.

FIG. 3 shows a tray 300 in tray load/unload area 202. Other trays may bein the tray load/unload area 202. An operator places the tray 300 on atray holder 302, wherein the holder 302 can accommodate two trays.Moreover, the holder 302 is attached to a tray pneumatic actuator 306,which, in turn, can be attached to a tray load/unload actuator 310. Morethan one tray pneumatic actuator may be connected to the trayload/unload actuator 310. For example, the actuator 310 may be connectedto two tray pneumatic actuators, wherein each of the tray pneumaticactuators is attached to a tray holder. This configuration allows forindependent movement of each tray holder using the separate traypneumatic actuators and for movement of all the tray holders using thetray load/unload actuator 310.

The tray 300 includes a tray lid (not shown in FIG. 3) and an RF tag301. HGAs 100 a-100 x are located on the tray. In one embodiment, thetray load/unload area 202 accommodates up to four trays and each traycan hold up to twenty HGAs. The trays used in the UHGAT are the sametrays that are used in operations previous and subsequent to the UHGAT.The UHGAT may be designed with two trays per side to enable trayload/unload from one side of the UHGAT while testing parts from theother side of the UHGAT. Simultaneous load/unload and testing enablesthe UHGAT to maximize units per hour.

FIG. 3 also shows an RF tag reader 328 placed below the tray 300. The RFtag reader 328 is attached to an actuator, which actuates the reader 328vertically to read the tray's RF tag. The first end effector 304 andsecond end effector 308 are attached to the automation structure aspreviously described. The first and second end effector's vacuums 322and 320 are located on the bottom surface of the first and second endeffectors 304 and 308, respectively. An optical sensor (not shown inFIG. 3) is placed below each tray to determine the tray's presence. Inone embodiment, the described structures accomplish the steps occurringin the tray load/unload area 202 in the following manner. An operatorplaces tray 300 in tray load/unload area 202, and the optical sensordetects the tray's 300 presence and notifies the UHGAT that the testercan select HGAs from tray 300. During tray loading, the RF tag reader328 reads the RF tag, which may contain information such as which HGAsshould be tested and whether the flex circuit 112 of the HGA is orientedto the left or the right. The orientation information is used toconfigure the UHGAT for the appropriate HGA testing processes, includingHGA placement on the précising and test nests, selection of theappropriate preamplifier to switch on, and the disc spin direction.Additionally, if an HGA fails the testing process, the RF tag may bemarked to indicate the HGA's failing status.

To initiate the automated testing process, an operator uses the userinterface on the display attached to the computer in the control area208. Once the automated testing process begins, it will continue as longas trays are loaded with HGAs to be tested. After initiation, anautomated pneumatic screwdriver 311 opens the tray lid. First endeffector 304 moves above the HGA 100 a to be tested, creates a vacuumwith the vacuum 322, and sucks the HGA's base plate 108 against firstend effector's bottom surface 323. Next, first end effector 304transports the HGA 100 a to précising area 204.

The steps that occur in the précising area 204 include moving the HGA100 a above and then lowering it onto the précising nest 210. As the HGA100 a is placed on the précising nest 210, pins align the HGA foreventual testing with the disc. Then the HGA 100 a is simultaneouslyde-shunted and headset at the précising nest 210, and it is subsequentlymoved to test area 206.

FIG. 4 shows the précising nest 210 in the précising area 204. HGA 100 ais positioned on the précising nest 210 so that the boss hole 110surrounds a boss hole pin 402 and the HGA's tooling hole 106 surrounds afront alignment pin 404. Both the boss hole pin 402 and the frontalignment pin 404 are tapered pins located on a top surface 401 of theprécising nest 210. FIG. 4 also shows the HGA's head 102 positionedbetween a pair of tapered pre-alignment guides 406 and extending beyonda lateral surface 403 of the précising nest 210. For future reference,the HGA's flex circuit 112 is viewed as oriented to the right when theflex circuit is angled to the right relative to an observer facing theprécising nest's lateral surface 403 from which the HGA's head 102protrudes.

Referring to FIG. 4, the précising nest 210 further includes two sets ofair actuated flex-on-suspension (FOS) aligners 408 a, 408 b and 408 c,408 d. Each set of FOS aligners 408 a, 408 b and 408 c, 408 d aresliding mechanisms that, starting from an open position, move towardseach other to push the flex circuit 112 to a predetermined de-shuntingposition, and constrain it from side-to-side motion. Using thenomenclature previously mentioned defining when a flex circuit is rightoriented, the right set of FOS aligners 408 a, 408 b moves flex circuitsthat are oriented to the right (see arrow A in FIG. 4), and the left setof FOS aligners 408 c, 408 d moves flex circuits that are oriented tothe left. A flex support is located on each set of the FOS aligners andprotrudes from the side designed to contact the flex circuit 112. Theflex supports 410 a, 410 b on the FOS aligners 408 a, 408 b arepositioned under the flex circuit 112 after the FOS aligners 408 a, 408b move the flex circuit 112 to its de-shunting position. A similar setof flex supports 410 c, 410 d are present on the FOS aligners 408 c, 408db and support the flex circuits that are oriented to the left.

Referring to FIG. 4 a, which shows an enlarged view of the FOS aligners408 a, 408 b and 408 c, 408 d in the closed position, the FOS alignersmove in concert when actuated. The FOS aligners' basic componentsinclude two rectangular bars, a first bar 409 a and a second bar 409 b.The set of FOS aligners 408 a, 408 c are part of the first bar 409 a,and the FOS aligners 408 b, 408 d are part of the bar 409 b.

When the bar 409 a is actuated in the direction of arrow A, the bar 409a moves along a path constrained by alignment pins 420, 421 andrespective cooperating angled slots 422, 424. This movement causes theFOS aligners 408 a and 408 c to move first laterally in the direction ofarrow A, and then to move in a direction B generally downward from theiroriginal position and normal to the arrow A. Simultaneous to themovement of the bar 409 a, the bar 409 b moves in a direction oppositethe arrow A. The movement of the bar 409 b is also constrained by thepins 420, 421 and respective cooperating angled slot 423 and a slot (notshown in FIG. 4). This constraint causes the FOS aligners 408 b and 408d to move first laterally in a direction opposite the arrow A, and thento move in the direction B. The lateral and downward movements of thebars 409 a and 409 b may release the flex circuit 112 from its clampedposition between the flex supports 410 a, 410 b if the circuit 112 isright aligned or the supports 410 c, 410 d if the circuit is leftaligned.

Conversely, when bar 409 a moves in a direction opposite the arrow A,the FOS aligners 408 a and 408 c move first laterally opposite the arrowA and then upward opposite the direction B. Simultaneous to the movementof the bar 409 a, the bar 409 b moves in the direction of the arrow A,and the FOS aligners 408 b and 408 d move first laterally in thedirection of the arrow A and then upward opposite the direction B. Thesemovements by the bars 409 a and 409 b may constrain and clamp the flexcircuit 112 between the flex supports 410 a, 410 b if the circuit 112 isright aligned or the supports 410 c, 410 d if the circuit is leftaligned.

The shunt tab 114 resides on the flex circuit 112 (see FIG. 1A) andelectrically shorts together an HGA head's readers and writers toprotect the HGA from electrostatic discharge damage. The shunt tab 114must be broken or removed before an HGA can be electrically tested.Breaking the shunt tab 114 must be done without damaging, bending ortwisting the flex circuit 112. Before breaking the shunt tab, it isfirst moved to the de-shunting position, then clamped between the flexsupports 410 a, 410 b or 410 c, 410 d (See FIGS. 4 and 4A). Referring toFIG. 4A, under the positioned shunt tab is a shunt tab hole 416, whichis a hole in the précising nest 210 that provides clearance for theshunt tab when it is folded down.

Referring to FIG. 4B, a de-shunt top plate 415 may be attached to apneumatic linear actuator (not shown) that moves the plate horizontallyin the direction of arrow C and another pneumatic linear actuator (notshown) that moves the plate vertically downward in the direction ofarrow D. After actuation, the de-shunt top plate 415 is positionedpartially above the flex circuit 112, and a de-shunt pin 400 a (See FIG.4C) on the underside 416 of the plate 415 is positioned above the shunttab. Referring to FIG. 4C, a right de-shunt pin 400 a is a small pinwith a chisel tip and is precisely located on the underside 416 of thede-shunt top plate 415 to punch the shunt tab 114 on the right-orientedflex circuit after the FOS aligners 408 a, 408 b and flex supports 410a, 410 b have constrained the flex circuit 112 and the shunt tab in thede-shunting position. In one embodiment, the pin 400 a may be roughlyone-third of the length of the shunt tab 114 and approximately the samewidth. In other embodiments, the pin 400 a may be different lengths andwidths. Similarly, a left de-shunt pin 400 b punches the shunt tab on aleft-oriented flex circuit retained by FOS aligners 408 c, 408 d andflex supports 410 c and 410 d. A compression foot 412 a is attached tothe de-shunt top plate 415 and completely surrounds the de-shunt pin 400a, while a similar compression foot 412 b surrounds the de-shunt pin 400b.

FIG. 4D is a diagram of one embodiment of the de-shunt pin 400 a usedfor de-shunting. The figure also shows the shunt tab 114 on the HGA,which may have a perforated side 426 farthest from the base plate 108,and the pin 400 a may be smaller than the shunt tab. This sizedifference permits variance in the positioning of the pin over the tabfor the de-shunting process. For example, the pin may be positioned sothat its outer diameter abuts a side 428 of the shunt tab closest to thebase plate or abuts the perforated side 426. When the diameter of thepin abuts the perforated side 426, the tip of the pin does not contactthe shunt tab at the perforated side because the tip is chiseled so thatit slopes away from the side 426. Instead, the tip contacts the shunttab at a point that may be more toward the middle of the shunt tab.Using a chiseled tip that contacts the shunt tab at a point away fromthe perforated side prevents distortion that could occur if a flat pindirectly contacted the perforated side 426. Although a flat pin may beused, the shearing force created by the pin on the perforation maydeform the HGA.

FIG. 4B also shows a flex circuit tail flattener 414 that is attached tofirst end effector 304 and is positioned above the flex circuit 112. Anelectromagnet 418 is attached to an pneumatic linear actuator (notshown) and may be actuated to a position where the electromagnet 418surrounds the HGA head 102 during the headset operation described below.

Referring again to FIG. 4B, in one embodiment the described structuresaccomplish the steps occurring in précising area 204 in the followingmanner. Once the first end effector 304 moves the HGA 100a from the trayload/unload area 202 along the X direction to a position above theprécising nest 210, it lowers the HGA 100 a along the Z direction onto aset of alignment pins. As shown in FIG. 4, the alignment pins includethe front alignment pin 404, the boss hole pin 402, and the frontpre-alignment guides 406 that set the skew, x, and y positions of theHGA 100 a.

As the HGA 100 a is lowered along the Z direction by the first endeffector 304, the HGA's boss hole 110 slips over the boss hole pin 402and the tooling hole 106 slips over the front alignment pin 404. As theHGA 100 a travels downward along the Z direction, the taper on thealignment pins 402, 404 pulls the boss hole 110 and the tooling hole 106into their proper locations. The tapered pins allow for somemisalignment of the HGA 100 a to the précising nest 210. The HGAalignment is completed while the HGA 100 a is lowered onto the pinscausing a relative motion between the HGA's base plate 108 and the firstend effector 304. This relative motion does not harm the HGA 100 a orthe first end effector 304 because the only force on the HGA 100 a whilebeing lowered onto the pins is due to the vacuum created by the firstend effector 304. The vacuum force is sufficient to hold the HGA 100 asecurely in the Z direction while still allowing horizontal translationalong the X direction as the HGA 100 a is pushed into position by thetapered pins. The précising nest's use of the boss hole 110 and toolinghole 106 for alignment makes the HGA testing process more accuratebecause these features also are used as an alignment datum when the head102 is attached to the HGA in production. Once the alignment iscomplete, the HGA 100 a is held firmly against the précising nest 210 bythe first end effector 304 to prevent any movement during the subsequentde-shunt and headset operations.

The précising nest's 210 two pre-alignment guides 406 are also taperedand provide a rough alignment of the HGA 100 a prior to it reaching thefront alignment pin during the downward movement along the Z directionof first end effector 304. The guides are used in the event that theinitial position of the HGA 100 a is far enough out of alignment thatthe tooling hole 106 would not slip over the taper of the frontalignment pin 404.

The alignment of the HGA is critical for the dynamic electrical testbecause the position of the HGA on the test nest 212 will affect thetest results. Aligning each HGA at the précising nest 210 eliminatesmisalignment caused by variation in HGA position in the tray andtray-to-tray differences. The précising nest ensures that every HGA isaligned relative to the travel axis of the coarse positioning system inexactly the same way, regardless of the HGA's alignment coming out ofthe tray.

After the HGA 100 a is aligned in the précising nest 210, thede-shunting process begins. Referring to FIG. 4B, the tail flattener 414is lowered down over the flex circuit 112 by first end effector 304 justin front of the shunt tab 114. Because the tail flattener 414 is springloaded, it remains down during first end effector's 304 movement and isin a downward position when placed over the flex circuit 112. When thetail flattener 414 is in place there is an approximate 0.005 inch gapbetween it and the précising nest 210. The tail flattener 414 gentlyconstrains the flex circuit 112 in the vertical direction but the gapallows the flex circuit 112 to float side-to-side without twisting.Without the tail flattener the de-shunt operation could causesignificant yield loss because the flex circuit tends to twist andbecome positioned incorrectly.

Because the flex circuit 112 can have an inherent twist to it andbecause the flex circuit 112 is allowed to move freely, the shunt tab114 is not always in an accurate, predetermined position on theprécising nest 210 for the de-shunting operation. To mitigate thisproblem, once the tail flattener 414 is in place, the FOS aligners 408a, 408 b move the flex circuit 112 into position to ensure that theshunt tab 114 is in the correct location for the de-shunting operation.

In this example, a right-oriented flex circuit is shown in FIG. 4. Aftermoving the flex circuit 112, the FOS aligners 408 a, 408 b constrain itfrom further side-to-side motion. Before the FOS aligners 408 a, 408 bbegin their movement, they are initially below a top surface 211 of theprécising nest 210 where the flex circuit 112 rests. This allows theflex circuit to land or slide freely during alignment without anyobstruction on top of the précising nest 210. As the FOS aligners 408 a,408 b move toward the flex circuit 112, the alignment pins 420, 421 andcooperating angled slots 422, 424 cause the aligners 408 a, 408 b torise vertically above the top surface 211 of the précising nest 210 sothey can push the flex circuit 112 to its final de-shunting position.

Referring to FIG. 4B, the de-shunt top plate 415 is then actuatedhorizontally above shunt tab 114 by a pneumatic linear actuator. Next,the de-shunt top plate 415 is rapidly lowered down by another pneumaticlinear actuator causing the de-shunt pin 400 a on the de-shunt top plate415 to contact the shunt tab 114. As the de-shunt top plate 415continues to travel downward, the pressure the de-shunt pin 400 a exertson the shunt tab 114 causes the shunt tab 114 to break along theperforated side 426 and fold down away from the flex circuit 112. Theshunt tab hole 416 shown in FIG. 4A provides clearance for the shunt tab114 when it is folded down.

To ensure that the flex circuit 112 does not bend or get pulled downinto the shunt tab hole 416 as the shunt tab 112 is punched, the flexsupports 410 a, 410 b are located on the FOS aligners 408 a, 408 b asshown in FIG. 4A. As the FOS aligners 408 a, 408 b slide towards theflex circuit 112, the flex supports 410 a, 410 b are positioned directlyunder the sides of the flex circuit 112 around the shunt tab 114. Theflex circuit 112 is also supported in front and back of the shunt tab114 by the précising nest 210.

To prevent buckling of the thin walls of the flex circuit 112 around theshunt tab 114 during the de-shunt operation, the compression foot 412 ais attached to the de-shunt top plate 415 as shown in FIG. 4C. Thecompression foot 412 a is spring-loaded and can travel in the verticaldirection. As the de-shunt top plate 415 travels downward towards theshunt tab 114, the compression foot 412 a compresses and holds the flexcircuit 112 before the de-shunt pin 400 a comes in contact with theshunt tab 114.

After de-shunting, the de-shunt top plate 415 and the FOS aligners 408a, 408 b move back to their unactuated positions. When the FOS aligners408 a return to their non-actuated position the tail flattener 414remains in its location but does not hold or impede the flex circuit 112from moving horizontally to its natural position. If the tail flattenerwere to keep the flex circuit from moving to its natural position, theprécising operation would likely fail due to the force that theconstrained flex circuit would apply on the HGA 100 a when the HGA wasremoved from the alignment pins.

At the same time the de-shunt operation occurs, the headset operationoccurs. Referring to FIG. 4B, a powerful electromagnet 418 attached to apneumatic linear actuator is actuated to a position where it surrounds aportion of the HGA 100 a that extends from the précising nest 210 andcreates a magnetic field around the HGA head 102. An operator cancontrol aspects of the headset operation through the UHGAT software suchas gauss level, duration, and pre/post-field collapse delays. After theheadset is complete, the electromagnet 418 is turned off and moved backto its un-actuated position. The materials of the précising nest 210,the first end effector 304, and the second end effector 308 can beselected to ensure that the electromagnet 418 does not leave a residualmagnetic field on the internal components of the UHGAT.

Although the de-shunt and headset operations occur in parallel,de-shunting may take less time than the headset, which allows thede-shunt operation to add zero additional test time. Performing theoperations in this manner can be a benefit compared to manual testingusing the intermediate mounting fixture because the latter methodtypically requires a separate process step for de-shunting. Also, usingthis method may ensure each HGA achieves a uniform gauss level andexposure time because the headset operation is entirely automated andcompleted inside the BGHAT.

Referring again to FIGS. 2-3, after completion of the alignment,de-shunt, and headset operations, the first end effector 304 is raisedto move the aligned HGA 100 a to the test area 206. As the HGA 100 a ismoved, the vacuum force created by the vacuum 322 of the first endeffector 304 maintains the HGA's alignment that was set on the précisingnest 210. In other embodiments, a mechanical device may be substitutedfor the vacuum 322 used to maintain alignment of the HGA duringplacement and removal from the précising nest 210. The device may holdthe HGA 100 a above the précising nest 210 and release it on thealignment pins located on the nest 210. The device may use a variety ofmethods to mechanically hold the HGA including clamping, hooking, andcarrying. After alignment on the nest 210, the device may recapture thealigned HGA. The device may then transport the HGA to the test nest 212while maintaining the HGA's alignment.

When the précising nest 210 is first attached to the UHGAT, it isaccurately aligned with the test nest 212 using gauges to ensure bothnests are in known locations so that the alignment performed at theprécising nest 210 will be accurate when the HGA 100 a is moved to thetest nest 212.

The steps that may occur in the test area 206 include placing the HGA100 a on the test nest 212 while maintaining the alignment set at theprécising nest 210 and preparing the HGA 100 a for testing with a disc810. The HGA's flex circuit 112 is flattened and a connection is madewith a preamplifier, and a second HGA 100 b is picked up from the tray300 and moved to the précising area 210. In parallel with the movementof the second HGA 100 b, the first HGA's head 102 is loaded to the disc810. A dynamic electrical test is performed. The second HGA 100 b ismoved from the précising area 210 to the test area 212, and the firstHGA 100 a is removed from the test nest 212. Next, the second HGA 100 bis placed on the test nest 212, and the first HGA 100 a is returned tothe tray 300 in the tray load/unload area 202. This process continuesuntil all the untested HGAs are tested.

FIG. 5 is one embodiment of a portion of the test area 206. The portionincludes the test nest 212, the collet assembly 500, a preamplifierassembly 502, a pivot bracket 503, and a clamp wing 606. The colletassembly 500 and the preamplifier assembly 502 may be attached to thepivot bracket 503. In one embodiment, the preamplifier assembly 502 mayhave gold contacts 602 that enable interconnection between thepreamplifier and the HGA's flex circuit pads 118. In another embodiment,a solderless connector may permit the interconnection. The clamp wing606 has clamp wing pins 614 that can engage slots 505 in the pivotbracket 503. The clamp wing 606 is part of a clamp wing assembly 600that is discussed later in greater detail.

FIG. 5A shows a cross-section of the test nest 212, which includes thecollet assembly 500 used to secure the HGA 100 a for dynamic electricaltesting with the disc 810. It is a small, air driven assembly thatapplies a downward force in the direction of arrow E on the HGA baseplate 108. The test nest 212 is very stiff with a low mass and isattached directly to a micro-actuator (not shown), which maintainsalignment of the HGA during clamping and needs no external tooling. Thecollet assembly 500 contains an integrated air piston 507 (See FIG. 5B),which includes an o-ring 506, a piston top 508 and a retainer 510 thatmove during actuation (See FIG. 5A). Surrounding the collet assembly 500is the collet housing 514, and on the top surface of the housing 514 isthe mounting area 524, where the HGA 100 a is placed. FIG. 5A also showsseals 522 located within the collet assembly 500.

FIG. 5B shows one embodiment of an exploded view of the collet assembly500. The assembly may be divided into three functional parts: colletfingers 504, the air piston 507, and a spreader pin 512 on the spreaderpin base 516. The collet fingers 504 may extend through the piston top508 of the air piston 507. In the embodiment shown, the assembly 500 ismade up of four individual fingers 504 a,b,c,d, however, it could bemade with three fingers, or as an integrated single flexure fingerassembly, depending on the size and shape of the article to be clampedinto position. In this embodiment, an o-ring 506 (shown in FIG. 5A) fitsaround the base of the fingers and provides the retracting force to keepthe fingers 504 from spreading when the air piston 507 is pushed upwardsin the direction of arrow F. The retainer 510 holds the fingers 504 inplace relative to the piston top 508 and enables their free verticalmovement on a spreader pin 512. The spreader pin 512 is stationary andis attached to a hollow spreader pin base 516.

FIG. 6 shows a clamp wing assembly 600 for making interconnect betweenthe HGA flex circuit 112 and a preamplifier in the test nest 212. Theclamp wing assembly 600 is made up of a linkage 604, an arrangement ofsprings 610, a linkage base 612, a clamp wing 606, and a clamp wing pad608 on an underside of the clamp wing 606. The linkage 604 has springs610 on each side of the linkage base 612 that spring load the linkage604 and hold the clamp wing 606 flat as it is moved over the flexcircuit 112. Referring to FIG. 6A, clamp wing pins 614 are located onthe front of the clamp wing 606 and engage slots 505 on a pivot bracket503 (not shown) located near the back edge of the HGA base plate 108.The pivot bracket 503 may not be attached to the test nest 212, whichpermits free movement of the nest 212 for micro-positioning during thetesting of the HGA. Instead, the pivot bracket 503 may be attached to apivot plate, which is discussed later in greater detail. In oneembodiment, the clamp wing pad 608 is located under the clamp wing 606and in line with an electrical contact, which may be an arrangement ofgold contacts 602 on a preamplifier assembly 502.

The gold contacts 602 may be cut from a single piece of conductivematerial, as shown in FIG. 6B. The conductive material may optionally bebrass, plated with nickel, and overlaid with gold. To fabricate thecontacts shown in FIG. 6B, the piece of conductive materials is cut ormolded to form separations between each contact 602. The contacts 602are maintained in spaced apart relation by thin break-away tabs 603.After the contacts 602 have been soldered to the printed circuit board(PCB) 630, the tabs are broken or cut off, leaving the individualcontacts 602 aligned with each other and the PCB 630.

In another embodiment, the electrical contact comprises a solderlessconnector that does not need to be soldered to the PCB 630. As shown inFIG. 6C, the connector 616 includes a housing 618 with at least twoapertures. A conductor 620, which includes a first end 624 and a secondend 628, may be partially contained within the housing 618. The firstend 624 may protrude from a first aperture 622 in the housing 618, andthe second end 628 may protrude from a second aperture 626. Theconductor 620 may be made from an elastic conductive material, such asfull-hard beryllium copper. The conductor 620 may be separated from theconnector housing 618 by an electrically insulative material. Thematerial selected for the conductor may be an elastic material that doesnot permanently deform when deflected, but substantially returns to itsoriginal form. The conductor 620 may also be gold plated to lower theresistance at the points where the conductor contacts the HGA and thepreamplifier assembly's PCB.

FIG. 6D is a more detailed view of the solderless connector 616 shown inFIG. 6C with optional features. The connector 616 has several conductors620 a-620 g with first ends 624 a-624 g and second ends 628 a-628 g thatmay protrude from apertures 622 a-622 g and 626 a-626 g, respectively.The flex circuit pads 118 are aligned with the first ends so that eachconductor may make contact with an individual pad when the HGA ispositioned for interconnection. The second ends are aligned with tracecontacts 632 a-632 g that are on the preamplifier's PCB 630. When theconnector is placed on the PCB 630, each second end may contact anindividual trace contact. In one embodiment, the first and second endsprotrude from apertures to contact the flex circuit pads 118 and thetrace contacts, respectively.

In an alternative embodiment shown in FIG. 6E, more than one conductormay contact the same flex circuit pad and corresponding trace contact.The housing may contain a pair of conductors 620 a,b mirrored about acenterline that is aligned with an individual flex circuit pad. Thefirst ends 624 a,b of the pair of conductors may protrude from a pair offirst apertures 622 a,b. The outer circumference of the apertures may beseparated by the width of the flex circuit pad less the diameter of eachaperture. The spacing permits both conductors to contact the flexcircuit pad at the same time when the pad is optimally aligned.

Use of the two conductors permits the flex circuit pad to contact thefirst end of a conductor even if the pad is not optimally aligned. Thisincreases the variance permitted in the positioning of the flex circuitpads on the connector. For example, if the flex circuit pad wasmisaligned in a direction to the upper left of FIG. 6B, the leftconductor 620 a of the conductor pair 620 a,b may make contact with thepad even if the misalignment prevents the right conductor 620 b from sodoing. A surface of the flex tail 112 that faces the connector 616 andsurrounds the flex circuit pads 118 may not be conductive becausemisalignment of the pads may cause one conductor of the pair to contactthe surface. If the surface was conductive, interconnection between thepreamplifier assembly and the conductive surface may cause a short tooccur.

The solderless connector 616 does not have to be soldered to the PCB 630to establish an interconnection between the HGA and the preamplifierassembly 502. Instead, the connector may be placed on the PCB 630without the use of solder. This makes removal of the connector 616 muchsimpler if it needs to be replaced. In some embodiments, the connector616 may be constrained by a device that holds it against the PCB 630.For example, as shown in FIG. 6E, a PCB cover plate 634 may be placedover the solderless connector 616. The cover plate 634 may have acorresponding aperture 636 that permits a portion 637 of the housing 618to pass through, while preventing another portion 635 from passing.

The cover plate 634 may be coupled to a structure that supports,surrounds, or is adjacent to the PCB 630 and may constrain or press theother portion 635 of the housing 618 against the PCB 630. In oneembodiment, the PCB cover plate 634 may be positioned over the PCB 630using alignment pins or dowels and corresponding apertures. The pins ordowels may protrude from a surface of the test nest 212, and the coverplate 634 may have apertures that are slipped over the pins or dowels.The cover plate 634 may also be clamped against the PCB 630 and screwedto the surface of the test nest 212 or to a PCB bottom cover plate thatis located between the PCB 630 and the test nest 212.

Referring to FIG. 6E, the housing 618 may have one or more alignmentfeatures, such as housing alignment element 638, that enables a smallconnection form factor and ready replacement. This irregularly shapedelement 638 permits precise alignment when the PCB cover plate 634 isused to secure the connector 616 to the PCB 630 and prevents incorrectinstallation of the connector 616. Correctly aligning the connector 616on the PCB also permits the connector 616 to be presented in a correctorientation to the flex circuit pads 118 because the pads may bepositioned to mate with the connector at a predetermined location. Inother embodiments, the housing may include housing alignment apertures640 that are used to align the connector 616. Alignment pins or dowelsmay protrude from the PCB 630, the test nest 212, and the PCB coverplate 634, or any combination of these, and the apertures 640 may slipover the pins to correctly locate the housing 618.

The housing 618 may be different shapes to accommodate different HGAgeometries. The housing size may depend on the length of the flexcircuit 112 and the number of flex circuit pads 118 on the circuit 112.For instance, if the flex circuit is short, the housing size may bedecreased to permit correct contact. If the flex circuit 112 has manypads 118, then the housing will have to accommodate the required numberof apertures and conductors needed to make contact with each of the pads118. The housing may advantageously be configured to accommodate andenclose the internal structure used to support, retain, and guide theconductors within the housing 618.

In another embodiment, pogo pins embedded in a cover, such as the PCBcover plate 634, may be used instead of the solderless connector 616.The cover plate 634 may be made of a malleable material, such asplastic, to permit embedding the pins. The pins are small metal tubswith a spring inside. On one side of the spring and partially protrudingfrom the tube is a pointed metal tip that digs into the PCB, and on theother side of the spring and partially protruding is a metal portionwith prongs that may contact the HGA flex circuit pads. When the coverplate 634 is aligned and placed over the PCB 630, the metal tip of thepins may contact the PCB trace contacts 632. The clamp wing 606 may thenpress the flex circuit pads 118 against the pronged portion of the pinsto establish electrical contact.

FIG. 7 shows the tail pusher 700 and tail flattener 414 both of whichare attached to the first end effector 304. The tail pusher 700 and tailflattener 414 have respective flanges 710 and 430 that contact eachother. The lower surface 712 of the tail pusher's flange 710 pressesagainst the upper surface 432 of the tail flattener's flange 430 so thatthe tail flattener 414 is necessarily raised when the tail pusher 700 islowered.

FIG. 8 shows the four bar loader (FBL) 800 that moves the HGA intoposition adjacent to the disc 810 for dynamic electrical testing of theHGA. The FBL 800 permits loading the head 102 to the disc 810 at aminimal pitch angle only limited by the HGA's geometry and may achievevarious radius and skew angels. The FBL 800 includes a pair of plates;one, the fixed plate 804, is fixed parallel to the disc surface, theother, the pivot plate 806, is allowed to pivot using a four bar linkage808. The pivot plate 806 is actuated with a tilt actuator 802 thatconnects the four bar linkage 808 and the pivot plate 806 to the fixedplate 804. The clamp wing assembly 600, pivot bracket 503, nest assembly212, and fine positioner (not shown in FIG. 8) are attached to the pivotplate 806 and tilt with the FBL 800. The whole assembly is typicallyattached to a moving stage 812 to enable movement to and from the disc810.

The FBL 800 enables positional accuracy and structural integrity. Thepivot plate 806 is aligned to the fixed plate 804 using precise pins(not shown) allowing for very accurate locating tolerances for the HGA.When the HGA is tested, the pivot plate 806 may be clamped to the fixedplate 804 using a variety of techniques, including but not limited to amechanical latch or latches or a vacuum pocket drawing the two platestogether. This gives excellent rigidity and isolates the pivotmechanisms from contributing to positioning error during test. It isimportant that the FBL 800 position the HGA base plate 108 parallel tothe disc during testing. To do this, the fixed plate 804 and the pivotplate 806 must be machined flat and parallel. In this way, the baseplate 108 parallelism is not dependent upon assembly techniques ortolerances.

Actuation is achieved with the use of pneumatic cylinders, though othertypes of actuators could be implemented. Pneumatic cylinders can providefast actuation at a low cost. Tilt velocity and end of travel impact iscontrolled with air pressure, flow controls, and dampers usingconventional techniques. One alternative is to use servomotors, at ahigher hardware cost, to provide more control of the tilt velocity.

In one embodiment, the described structures accomplish the stepsoccurring in the test area 206 in the following manner. The first endeffector 304 moves the HGA 100 a from the précising area 204 to aposition above the test nest 212. It then lowers the HGA 100 a onto thetest nest 212 and presses it against the test nest 212. During thisprocess, the HGA 100 a maintains the alignment set on the précising nest210.

Referring to FIGS. 5 and 5A, when the HGA 100 a is lowered, the bosshole 110 slips over the extended fingers 504 of the collet assembly 500.In their extended state, the fingers 504 are contracted because theo-ring 506 pulls the fingers together and the spreader pin 512 does notexert pressure through the center of the four fingers when they are inthe extended position. When the fingers 504 retract, the spreader pin512 forces the fingers 504 open, and the fingers grab the base plate 108and pull it down tight against the surface of the collet housing 514. Asthe fingers 504 pull down against the base plate 108, angled protrusions509 on their respective tips 511 catch the angled surface 110 a (FIG.1A) on the inside of the boss hole 110 and pull the base plate 108 tightagainst the mounting area 524. This process permits the collet assembly500 to hold the HGA without disturbing the alignment previously set onthe précising nest 210.

The application of vertical force is controlled by air pressure.Referring to FIG. 5A, the pressurized air fills a lower space 518 whichcauses the piston top 508, retainer 510, and the fingers 504 to move up.Downward movement occurs when the pressurized air fills an upper space520 and the air in the lower space 518 is permitted to exhaust to theambient environment. The downward movement causes the fingers 504 tocontact the spreader pin 512, which creates an outward pressure on thefingers 504 causing them to spread. In this way, the fingers are spreadas they are lowered towards the surface of the collet housing 514 thatserves as the HGA mounting area 524. To capture and hold the HGA 100 aand maintain its precise alignment, the fingers 504 need to expandprecisely the same amount of distance and with the same amount of force.With the small size of the collet assembly 500, the independent fingers504 may permit a better dimensional consistency between the fingers thanif the fingers were cut from a single piece of material.

The collet fingers 504 open up and then pull down, providing therequired downward force with minimal radial force. There could be avariety of applications for the collet assembly 500, and its size may bescaled up or down depending on the size object to be secured. Thepneumatics can be replaced with springs for actuation with a finger orother mechanical means. In the embodiment discussed herein, the colletassembly 500 is fabricated with four individual fingers with an o-ringto provide the retracting force. However, the individual fingers may bedesigned based on what size or type of HGA is being clamped. Forinstance, in a slightly larger scale, the collet could be one piece,where the fingers were flexures and provided their own retracting force.

After the collet assembly 500 has secured the HGA 100 a to the mountingarea 524, the HGA's flex circuit 112 is interconnected with thepreamplifier's gold contacts 602 (FIG. 6A). The tail pusher 700 on firstend effector 304 is actuated to move the HGA flex circuit 112 down onthe gold contacts 602. Here, the tail pusher 700 helps align the flexcircuit to the preamplifier's gold contacts 602 for interconnection. Asshown in FIG. 7, when the tail pusher 700 is actuated downward, the tailflattener 414 moves up allowing clearance for the clamp wing 606. Thetail pusher 700 also pushes the flex circuit 112 down so that the clampwing 606 does not catch on the circuit 112 as it is actuatedhorizontally.

Referring again to FIG. 6A, after the clamp wing 606 is actuated abovethe flex circuit 112, it presses the flex circuit pads 118 (See FIG. 1A)against the gold contacts 602. The clamp wing assembly 600 may benecessary because making an automated electrical connection requirespulling the flex circuit 112 down against the gold block contacts 602 ina consistent manner. When pulling down the flex circuit 112, the circuit112 first needs to be contacted near the HGA base plate 108, and presseddown with an even pressure over the length of the flex circuit 112. Theclamp wing pins 614 on the front of the clamp wing 606 engage slots 505on the pivot bracket 503, which may be mounted to the pivot plate 806.The clamp wing 606 is then actuated down against the flex circuit in arolling motion, where the clamp wing pins 614 are engaged in the slotsand the clamp 606 rotates in a downward circular motion around the axiscreated by the pins 614.

The clamp wing pad 608 is located under the clamp wing 606 and may becomposed of compliant materials including electrostatic dissipativeelastomers. The pad 608 is in line with the gold contacts 602 andapplies a compliant force to the flex circuit pads 118 to press themagainst the gold contacts 602. The initial engagement of the pins 614followed by the clamp wing's downward actuation allows the flex circuit112 and pads 118 to float during the flattening out of the flex circuit112, which helps remove a great deal of the flex circuit's 112positional error. In this way, the clamp wing 606 presses and holds theHGA flex circuit 112 onto the preamplifier's gold contacts 602, whichestablishes a connection.

Additionally, when interconnecting the flex circuit 112 with the goldcontacts 602 any positional errors of the flex circuit 112 must becorrected or compensated. Another way to overcome the positional errorsof the flex circuit 112 is to make the area with the gold contacts 602much larger than the flex circuit pads 118 that interconnect with thecontacts 602. By using large flat gold contacts 602 with an area thatcovers the tolerance range of the flex circuit location, one may ensurethat the gold contacts 602 and the flex circuit pads 118 contact eachother when they are pressed together. This type of interconnect aidsautomation because it is very tolerant to positional flex circuiterrors.

The compressive force may be applied to the flex circuit 112 nominallycentered over contact pads 118 with a compliant material, such as theclamp wing pad 608, so that the force can overcome errors in the heightsof multiple contacts as well the height differences of the flex circuitlayers. The clamp wing pad 608 may be comprised of an array of posts.The size of the posts may be half the size of the of the contact pads118 to ensure that at least one full post may press the contact pad 118against the gold block 602. Using posts of this size maximizes thepressure of the contact pad 118 against the gold block 602 at a minimumoverall force to compress the compliant pad 608. The reliability of theelectric circuit may depend upon the pressure of the contact pad 118against the gold block 602.

In other embodiments, a post with a smaller diameter may be used toincrease the post density on the contact pad 118. Larger posts may alsobe used. Alternatively, ribs may be used instead of posts. The ribs maybe alternating stripes of high and low regions of the clamp wing pad 608that can make lines of contact across the width of the contact pads 118when the compressive force is applied. In another embodiment, the clampwing pads 608 may have a waffle pattern, where the there may be 2patterns of ribs aligned perpendicular to each other to create a wafflepattern on the clamping wing pad 608. The waffle pattern clamp wing pad608 may require a greater compressive force to achieve reliable contactbetween the contact pad 118 and gold block 602, but may have a lowermanufacturing cost.

The clamp wing assembly 600 may make contact between the connector 616described in FIGS. 6C-6E and the flex circuit pads 118 with a methodsimilar to that described for the gold block 602. Additionally, when theclamp wing pad 608 applies compressive force to press the flex circuitpads 118 against the first end 624 of the connector's conductor 620, thefirst end 624 may deflect or bend. The deflection may be flush with thesurface of the housing 618 that faces the pads 118 to ensure an adequateconnection is established. Using an elastic material for the conductorcauses it to oppose the force created by the clamp wing pad 608, and thegreater the deflection of the conductor, the greater the oppositionforce. In turn, the opposition force can permit a reliable contactbetween the flex circuit pads 118 and the deflected conductor 620. Theuse of an elastic material in constructing the conductors 620 permitsthe conductor to return to substantially its original position after theflex circuit 212 is removed, so that the connector 616 may be used maytimes before it has to be replaced.

Once the HGA 100 a is clamped by the clamp wing assembly 600 and itsorientation is set, first end effector 304 releases HGA 100 a andreturns to the tray load/unload area 202 to pick up a second HGA 100 band moves it to the précising area 210, where the second HGA 100 bbegins the processes described for the first HGA 100 a.

As shown in FIG. 8, the FBL 800 is used to load the HGA 100 a to thedisc 810 while the second HGA 100 b is picked from the tray load/unloadarea 202. Referring to FIG. 8A, the FBL 800 tilts the pivot plate 806down relative to its position shown in FIG. 8 in order to move the HGA100 a below the surface of the disc 810. Next, as shown in FIG. 8B, themoving stage 812 on which the FBL 800 is mounted moves the HGA 100 a toa load radius under the disc 810, and as shown in FIG. 8C, the pivotplate 806 is tilted up to a test radius. The HGA is then tested with thedisc 810, and the results are read and analyzed by the UHGAT software.After the UHGAT performs the testing on the HGA 100 a, the FBL's movestage 812, moves the HGA to an unload radius, the FBL 800 tilts pivotplate 806 down, and the FBL 800 returns to its original location.

Use of the four bar linkage 808 on the FBL 800 enables the projection ofa hinge pivot point into space. Proper choice of linkage 808 enablesputting a virtual pivot point near the bend of the load beam 104 (FIG.1B). Additionally, as shown in FIG. 8C, the preamplifier assembly 502,including the contacts 602, are not located on the same plane as thebase plate 108. Instead, they are on a plane sloped away from and belowthe plane of the base plate relative to the disc 810. In this position,the preamplifier assembly does not limit the loading of the HGA becauseit is not in a location where it could contact the disc. The projectionof the pivot point and the location of the preamplifier's parts enableloading the HGA 100 a with the head 102 at a very shallow angle that isonly limited by the geometry of the HGA.

The FBL design may also be flexible. For instance, the linkages may besized to locate the pivot where a wide range of HGA geometries can beaccommodated. However, if a different style of HGA or HGA attachmentmechanism is used, a simple change of the linkages can move the virtualpivot to a new optimum location.

After the HGA 100 a has been tested, first end effector 304 moves thesecond HGA 100 b from the précising area 204 to the test area 206, andthe first HGA 100 a is removed from the test nest 212 by the second endeffector 308. The second end effector creates a vacuum force with thevacuum 320 (FIG. 3) to retain the HGA's base plate 108 on the bottomsurface of second end effector 308 and the collet assembly releases theHGA 100 a by extending the fingers 504 upward allowing the base plate108 to slip over them. Then the second end effector 308 removes thefirst HGA 100 a, and the first end effector 304 places the second HGA100 b on the test nest 212. Loading and unloading the HGAs to and fromthe test nest 212 takes less than 2.5 seconds, which is far faster thanany manual operator.

The first end effector 304 and the second end effector 308 are thenactuated back to the tray load/unload area 202 and the first HGA 100 ais returned to the to the tray 300. If the HGA 100 a fails, theelectrical test the tray's RF tag can be marked to indicate the failure.The described process continues until all the untested HGAs are tested.

When testing the HGA with disc 810, an optional disc flutter controldevice 900 shown in FIG. 9 may be used to mitigate errors caused by discflutter. Internal or external sources, such as internal spindlevibrations or external windage and acoustic vibrations, may excite thedisc 810 and cause disc flutter. The flutter control device 900 reducesdisc flutter by including a removable shroud 902 in close proximity tothe disc 810. This feature provides a cushioning force and in effectoperates as a stiff virtual spring that connects the disc 810 to thecover, which reduces the results of disc flutter including asynchronousradial runout.

FIG. 9 shows the optional disc flutter control device 900 in use withthe disc 810. The removable shroud 902 is positioned so that theshroud's underside 903 is shown. The shroud 902 may be removed to permitconvenient access to the disc adapter 916 when seating the disc 810 orwhen the surrounding structures require service. During operation, thecircular portion 904 of the shroud 902 may be above the disc 810, whichmay require testing HGA heads on the bottom surface of the disc 810. Inoperating position, the shroud 902 is attached to a base 906, which isattached to a riser 908. A spindle motor 910 is also mounted to theriser 908 via a spindle mounting flange 912. The triangular spindlemounting flange 912 may be surrounded on two sides by the base 906. Theside that is not surrounded faces the four bar loader 800 and providesthe loader 800 access to the disc 810. A disc adapter 916 is attached tothe spindle motor 910, and the adapter 916 holds the disc 810 fortesting. The disc 810 may be placed on the adapter 916 by passing thedisc's center aperture through the protruding portion of the adapter916.

FIG. 10 shows a section view of one half of the disc flutter controldevice 900. The figure illustrates the gaps between the structures,which define an air cushion between the disc 810 and the shroud 902. Theside of the disc 810 that defines its outer circumference is the radialdisc side 918, and the disc side that is perpendicular to the radialdisc side and that faces the shroud 902 is the axial disc side 920.Correspondingly, the gap between the radial disc side 918 and the shroud902 is the radial disc gap 922, and the gap between the axial disc side920 and the shroud 902 is the axial disc gap 924. The gap between theside of the disc adapter 916 and the shroud 902 is the disc adapter gap926.

Referring to FIG. 11A, when the spindle motor 910 rotates the disc 810,the motor 910 may create vibrations 1 that excite the disc 810 and causedisc flutter. In addition, air flow 2 around the disc 810, as well asturbulence 3 near the radial side 918 of the disc 810, create pressurevariations and causes random structural excitation forces to be exertedon the disc 810, which in turn cause excitation of disc modes.

However, as shown in FIG. 11B, the shroud 902 causes the air flow aroundthe disc 810 to travel in the direction of arrow G. The small size ofthe gaps 922, 924, 926 reduce and smooth air flow near the disc 810.This reduced flow reduces turbulence near the disc 810, and theresulting reduced pressure against the disc reduces excitation of discmodes. The narrow gaps 922, 924, 926 create an air bearing that acts asa stiff virtual spring between the shroud 902 and the disc 810. Thevirtual spring constrains the movement of the disc 810 relative to theshroud 902, which reduces the amount of disc flutter in the disc 810caused by spindle motor vibrations, which reduces spindle runout andimproves the track per inch performance of the test system.

To create a stiffer virtual spring that provides a greater reduction indisc flutter, the axial gap 924 should be as small as possible withoutpermitting contact between the shroud 902 and the disc 810. Moreover,the adapter gap 926 and the radial disc gap 922 also affect the discflutter. A smaller adapter gap 926 substantially reduces the discflutter present at the outer edge of the disc 810, while a smallerradial disc gap 922 substantially reduces the disc flutter present atthe inner edge of the disc 810. By adjusting the thickness of each ofthe gaps 926 and 922, one can achieve uniform suppression of discflutter at both the inner and outer disc edges.

FIG. 11B also illustrates a vacuum created by the spinning disc 810. Inone embodiment, the vacuum draws external ambient air over the axialdisc side 920 as shown by the arrows. In other embodiments, pressurizedgas sources could provide the gas present in the gaps. The gas alsocould dynamically flow over the axial disc side 920 or remain in astatic state in the gaps.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A method of controlling disc flutter, comprising: placing a surfaceof a shroud in close proximity to a surface of a disc, wherein the discis located on a spindle; rotating the disc using the spindle; andintroducing a gas into a gap between the surface of the shroud and thesurface of the disc.
 2. The method of claim 1, wherein the gas isintroduced into the gap by a pressurized gas source.
 3. The method ofclaim 1, wherein the placing includes positioning the surface of theshroud as close as possible to the surface of the disc without makingcontact between the surface of the shroud and the surface of the disc.4. The method of claim 1, wherein the placing further comprises placinga second surface of the shroud in close proximity to a radial surface ofthe disc, the radial surface being located on an outer edge of the disc.5. The method of claim 4, wherein the placing further comprises placinga third surface of the shroud in close proximity to a surface of thespindle, the surface of the spindle being located perpendicular to thesurface of the disc.
 6. The method of claim 5, wherein the placingincludes adjusting a distance between the second surface and the radialsurface and between the third surface and the surface of the spindle toproduce equal suppression of disc flutter on outer and inner edges ofthe disc.
 7. The method of claim 1, wherein the gap provides an airbearing to constrain movement of the disc relative to the shroud.
 8. Themethod of claim 1, wherein the surface of the disc is a top surface ofthe disc.
 9. The method of claim 8, further comprising testing a headgimbal assembly on a bottom surface of the disc.
 10. The method of claim9, wherein the testing includes dynamic electrical testing of the headgimbal assembly on the bottom surface of the disc.
 11. A system forcontrolling disc flutter, comprising: a rotating spindle; a rotatingdisc located on the spindle; and a shroud having a surface in closeproximity to a surface of the disc, wherein a gas is introduced into agap between the surface of the shroud and the surface of the disc. 12.The system of claim 11, further comprising a pressurized gas source thatintroduces the gas into the gap.
 13. The system of claim 11, wherein thesurface of the shroud is as close as possible to the surface of the discwithout making contact between the surface of the shroud and the surfaceof the disc.
 14. The system of claim 11, wherein a second surface of theshroud is in close proximity to a radial surface of the disc, the radialsurface being located on an outer edge of the disc.
 15. The system ofclaim 14, wherein a third surface of the shroud is in close proximity toa surface of the spindle, the surface of the spindle being locatedperpendicular to the surface of the disc.
 16. The system of claim 15,wherein a distance between the second surface and the radial surface andbetween the third surface and the surface of the spindle is optimized toproduce equal suppression of disc flutter on outer and inner edges ofthe disc.
 17. The system of claim 11, wherein the gap provides an airbearing to constrain movement of the disc relative to the shroud. 18.The system of claim 11, wherein the surface of the disc is a top surfaceof the disc.
 19. A system comprising: a rotating spindle; a rotatingdisc mounted to the spindle; and a means for controlling disc flutter ofthe rotating disc.
 20. The system of claim 19, further comprising: ahead gimbal assembly; and a loader mechanism that loads the head gimbalassembly on the rotating disc for testing the head gimbal assembly.